HR: 0800h
AN: SM11A-0314    [Abstracts]
TI: Travel time of impulsive signals in the magnetosphere: Modeling and observations
AU: * Chi, P J
EM: pchi@igpp.ucla.edu
AF: UCLA Institute of Geophysics and Planetary Physics, Box 951567, Los Angeles, CA 90095- 1567, United States
AU: Russell, C T
EM: ctrussell@igpp.ucla.edu
AF: UCLA Institute of Geophysics and Planetary Physics, Box 951567, Los Angeles, CA 90095- 1567, United States
AU: Angelopoulos, V
EM: vassilis@ssl.berkeley.edu
AF: UCLA Institute of Geophysics and Planetary Physics, Box 951567, Los Angeles, CA 90095- 1567, United States
AB: The calculation of travel time for impulsive signals has many uses in magneotspheric physics, such as understanding the propagation of sudden impulses, helping identify the causes of substorm onsets, and inferring the global plasma density and temperature from inverting the signal arrival time at multiple locations. Because impulsive signals can propagate rapidly as MHD waves, it is necessary for calculations and observations to have a time resolution of the order of one sec to yield useful results. To avoid time-consuming global simulations at this high cadence, we have developed a numerical model that focuses on wavefront construction to compute the travel time of impulsive signals. Following the Huygens principle, the algorithm allows the user to define the shape of the initial impulse and tracks the first arrival of wavefront in two dimensions. We will demonstrate, in both equatorial and meridian planes, how the wavefront of sudden impulses propagates tailward from the dayside magnetopause and how the wavefront of substorm onsets in the magnetotail evolves as it propagates earthward. We compare our calculations with the magnetic field observations from the armada of satellites, including Polar and THEMIS, in orbit, as well as the data from various ground magnetometer networks such as McMAC, THEMIS-GBO/EPO, and CARISMA.
DE: 2109 Discontinuities (7811)
DE: 2740 Magnetospheric configuration and dynamics
DE: 2752 MHD waves and instabilities (2149, 6050, 7836)
DE: 2753 Numerical modeling
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting